Ossa is a product of a breeding and selection program for outdoor pot mums (garden mums) which had the objective of creating new chrysanthemum cultivars with a decorative type flower, a natural season flower date around 1-4 September; blooming for a period of 7 weeks. The new plant of the present invention comprises a new and distinct cultivar of Chrysanthemum plant xe2x80x98OSSAxe2x80x99 is a seedling resulting from the open pollination among groups of chrysanthemum cultivars maintained under the control of the inventor for breeding purposes. The new and distinct cultivar was discovered and selected as one flowering plant by Rob Noodelijk on a cultivated field in Rijsenhout Holland in September 1996. The plant has been asexually reproduced by cuttings in greenhouses at Rijsenhout Holland. The new cultivar has been found to retain its distinctive characteristics through successive propagations.